In an automobile, the shortage of air pressure in a tire tends to cause steering in the wrong direction and overheating or abrasion of the tire by bending, which will seriously shorten the life of the tire. To prevent these problems, there has been provided an apparatus to sense shortage of air pressure in the tire and generate a signal to the driver indicating the same.
However, such an apparatus senses the air-pressure drop and provides a signal only when the air pressure drops to a fixed level, and it is almost impossible to keep the air pressure in the tire within a desired range if an initial air pressure is set considerably high to serve a special purpose or at the driver's wish. Further, the apparatus is not very reliable. For example, when a tire runs hot while driving, air pressure in the tire generally rises, and in the case where the risen air pressure is relatively lower than the initial air pressure setting, the apparatus ofter may not sense it.
An object of the present invention is to provide an apparatus which can sense a predetermined amount of pressure drop in a tire from an initial air pressure setting and provide a signal to the driver regardless of the level of the initial air pressure.
Another object of the present invention is to provide an apparatus which can sense a predetermined amount of pressure drop in a tire from an initial air pressure setting without being affected by overheating of the tire.
Still another object of the present invention is to provide an apparatus for sensing an air pressure drop in a tire which can be applied in place of a known air valve on the tire, and operate reliably.
According to the present invention, there is provided an apparatus capable of keeping air pressure in a tire at a desired level to serve a special purpose or to satisfy the driver's preference.